1940 recipe for macaroni cheese

Well, it's hard to find now, but yeah. American cheese was originally just a mild, unaged cheddar back in the 1800s until the early 1900s. It wasn't the processed cheese that gets the name now.

That change started after 1916, which was when the Kraft process came around.

At the time, anecdotally, the processed cheese was a lot firmer than the velveeta type of process cheese that came later on. It was pretty much the same mild, unaged cheddar that had been pasteurized then mixed with whatever emulsifier was used (I think it was sodium citrate, but don't bet money on my memory).

Processing eventually got shifted into what we know today, where the starting point uses other dairy products.

But! The prepackaged slices that people think of as American Cheese, the default version, isn't the same that you'll find in blocks. That stuff is mixed and then wrapped hot, only cooling once it's inside the little plastic packets. So it's much softer than than the blocks. The blocks are quite slicable, and you can find presliced packages of it in stores, usually billed as "deli style" or something similar. It may or may not contain more actual cheese than the the wrapped slices, but it is firmer.

You can, however, sometimes find American Cheese that's closer to the original where it's just pasteurized and emulsified, then formed into blocks. I can't recall the brand we get offhand, my brain isn't in full gear yet. But if you check the labelling, it'll have only three or four ingredients. It'll be labeled as "pasteurized process American cheese" rather than "pasteurized process American cheese food" (though I don't agree the term food applies to that shit, it's still better than the stuff labeled as "pasteurized process cheese product" which has no actual cheese in it).

The first two versions are legally regulated, and have standards that are supposedly met. The first has to be made from actual cheese, but will contain multiple cheeses. The second only has to have 51% cheese. Anything else can be made of what the fuck ever, and isn't worth buying, imo.

If the label says only American cheese, it has to have been made by pasteurizing and emulsifying cheddar, Colby, cheese curd, granular cheese, or a combination of those. In other words, it's actually cheese, and the only extras are the emulsifiers. Again, this is a legal standard. The process and emulsifiers are regulated as well, but fucked if I'm looking them up lol.

But, other than the ones labeled as cheese product, they all start with real cheese.

This all comes back to what you were wondering. Back in the forties, what was on the market was still what would be labeled as American Cheese under current regulations, so you could expect a fairly firm block that could be shredded very easily even at room temp. Mild cheddar does stick a little to a grater, and the actual American Cheese (as opposed to a cheese from America, because we have plenty of other cheeses) is sometimes a little less sticky when shredded. If the block is refrigerated, it's as easy to shred as any mild cheddar.

All of that seems overly involved, but there are similar product regulations all over the world. You wanna see some complicated cheese regulations, check out France!

All of the various types get called American Cheese, but the recipe here would not be using the kinds that didn't exist until (iirc) after the war.